Improving the long-term stability of bismuth alloy well plug systems

碳氢化合物资源开发是加拿大经济的关键驱动力。 这导致有害气体的排放、大气中二氧化碳的积累以及威尔斯地下水污染的可能性。 无论是降低污染、采用水力压裂还是将二氧化碳封存在地下，对旧井和多余井眼进行战略性封堵都至关重要。 在2012年阿尔伯塔省大约40万口威尔斯油井中，需要适当封堵的威尔斯油井数量可能远远超过5万口，而且这一数字还在急剧增长。 尽管阿尔伯塔在管理地下水意外污染和特别有害气体释放的坚韧标准方面处于世界领先地位，但封堵技术还没有跟上需要退役的大量威尔斯井的步伐。 Seal Well Inc.，一家位于艾伯塔省的公司，已经申请了一项基于铋锡合金的替代井筒封堵技术的专利，该技术的安装成本更低，同时比目前的方法可靠得多。 为了使这项技术适应日益增长的高腐蚀性加压CO2的使用，以提高石油采收率和CO2封存，有必要证明Bi-Sn合金和周围的钢将具有形成永久塞所需的使用寿命。 该项目的重点是确定Bi-Sn合金/钢系统在实际井下条件下的腐蚀敏感性，并通过组合策略解决酸性气体侵蚀所遇到的腐蚀问题。 首次将缓蚀剂和除氧剂应用于Bi-Sn/钢体系的方法将在CO2饱和盐水中开发和测试。 此外，还将对Bi-Sn合金的表面结构进行改性以使其更耐腐蚀，并将探索电解阴极保护和在Bi-Sn表面上添加保护性Bi涂层的方法。 这项工作的成果将是在恶劣的地下条件下显著延长Seal Well技术的使用寿命，从而遏制世界各地严重加剧的污染问题，以及培训大量人员掌握腐蚀技术。

Hydrocarbon resource development is a key driver of the Canadian economy. This has led to the emission of harmful gases, the build-up of carbon dioxide (CO2) in the atmosphere, and the potential for contaminating ground water from wells. Whether lowering pollution, employing hydraulic fracturing, or sequestering CO2 underground, strategic plugging of old and redundant wellbores is critical. Of the roughly 400,000 wells in Alberta in 2012, the number of wells that need to be properly plugged could well exceed 50,000, and this number is growing dramatically. Although Alberta leads the world in tough standards governing the unintended contamination of ground water and release of particularly harmful gases, plugging technologies have not kept pace with the vast number of wells that need to be retired. Seal Well Inc., an Alberta-based company, has patented an alternative wellbore plugging technology based on a bismuth-tin (Bi-Sn) alloy that should be less costly to install, while being far more reliable than current methods. To adapt this technology to the growing use of highly corrosive, pressurized CO2 for enhanced oil recovery and CO2 sequestration, it is necessary to demonstrate that the Bi-Sn alloy and the surrounding steel will have the useful service life needed to form a permanent plug. The focus of this project is to determine the corrosion susceptibility of the Bi-Sn alloy /steel system under realistic down-hole conditions and address corrosion issues encountered from acid gas attack through a combination of strategies. For the first time, a method of applying corrosion inhibitors and oxygen scavenger to Bi-Sn/steel systems will be developed and tested in CO2-saturated brine. Also, the surface structure of the Bi-Sn alloy will be modified to make it more corrosion resistant, and methods of electrolytic cathodic protection and addition of protective Bi coatings onto the Bi-Sn surface, will be explored. The outcome of this work will be the significant extension of the useful service life of the Seal Well technology under harsh underground conditions, thus containing a significantly escalating pollution problem throughout the world, as well as the training of a large number of personnel in corrosion technologies.